Quick-action clamping device used in rotary cylinders of printing machines

ABSTRACT

A quick-action clamping device for use in a rotary cylinder of a printing machine for clamping flexible printing plates including a stationary clamping bar assembly and a displaceable bar assembly. The latter may be selectively held in a position which tensions the flexible printing plate and in a position which does not tension the flexible printing plate. A latch means is provided to engage said displaceable clamping assembly and retain the latter in its non-tension applying position.

United States Patent 1 1 Jahn [451 July 1,1975

[ QUICK-ACTION CLAMPING DEVICE USED IN ROTARY CYLINDERS OF PRINTING MACHINES [75] Inventor: Hans-Georg Jahn,Wiesloch,

Germany [731 Assignee: Heidelberger Druckmaschinen Aktiengesellschait, Heidelberg, Germany [22] Filed: Apr. 18, 1973 [21] Appl. N0.: 352,196

[30] Foreign Application Priority Data Apr. 21, 1972 Germany 2219546 [52] US. Cl l0l/4l5.l; 101/378 [51] Int. Cl 1. B4" 27/12 [58] Field of Search l0l/415.l, 378

[56] References Cited UNITED STATES PATENTS 1.107512 8/1914 Gardner .1 l()1/4l5.l X 1.391,]17 9/1921 Huebner .l l()1/415.l 2.056.205 10/1936 O'Hara s lOl/4l5.l 3,017,830 1/1962 Penner ICU/415.1

3,107.60) 10/1963 Haramija 101/378 3,202,098 8/1965 Keeler l v t .1 l0I/4l5.l 3,203.346 8/1965 Norton et a1. r. lOl/4lS.l X 3.424985 1/1969 Beisel l. l0l/4l5.l X 3,583,318 6/1971 Stevenson 1 lOl/4l5.l 3,696,744 10/1972 Etchell 4. l()l/4l5.l

FOREIGN PATENTS OR APPLICATIONS 1,523,531 3/1968 France l0l/4l5.l

Primary Examiner-Edgar S. Burr Assistant ExaminerPaul .l. Hirsch Attorney, Agent, or Firm-Herbert L. Lerner 57] ABSTRACT A quickaction clamping device for use in a rotary cylinder of a printing machine for clamping flexible printing plates including a stationary clamping bar assembly and a displaceable bar assembly. The latter may be selectively held in a position which tensions the flexible printing plate and in a position which does not tension the flexible printing plate. A latch means is provided to engage said displaeeable clamping assembly and retain the latter in its non-tension applying position.

2 Claims, 3 Drawing Figures MTFHTFH JUL '1 1975 8 92.17 9

SHEET 2 QUICK-ACTION CLAMPING DEVICE USED IN ROTARY CYLINDERS OF PRINTING MACHINES The invention relates to a quick-action clamping device as used in rotary cylinders of printing machines for clamping flexible printing plates. A stationary clamping bar assembly and a displaceable clamping bar assembly which can be displaced along a secant are disposed in a cylinder channel. The displaceable clamping bar assembly may be selectively held in a position which tensions the printing plate or in a position which does not tension the printing plate.

lt is an object of the present invention to permit clamping of new offset plates on a plate cylinder quickly and with a minimum of means.

German Pat. No. l,265,l63 corresponding to US. Pat. No. 3,424,085 described a quick-action clamping device in which the displaceable clamping bar assemblies are guided laterally and can be moved by clamping studs into a position for tensioning the plate and by an eccentric into a position which does not tension the plate. However, disadvantages of this known device are that actuation of the eccentrics is time-consuming, plates of different length cannot be clamped, and the plates, if required, cannot be clamped firmly on the cylinder additionally by screw means.

It is an object of the present invention to simplify and accelerate the clamping process still further. The above-mentioned objective is achieved by the provision of at least two guide rods which are fastened to the rear side of the displaceable clamping bar assembly and which are continuously under spring tension in the tensioning direction of the plate. A latch is pivoted centrally, as viewed in the lengthwise direction of the cylinder channel. about an axis extending perpendicularly to the axis of rotation of the cylinder, and this latch holds the displaceable clamping bar assembly in the nontensioning position against a stop edge extending in the longitudinal direction of the cylinder channel.

After the ends of the plate are clamped, it is only necessary to turn the latch away by means of the clamping key, and the spring-loaded guide rods clamp the plate on the plate cylinder ready for printing. Flexible lithographic plates of different length are offered on the market for use on the same cylinder diameter. These plates differ in length by a few centimeters. Taking this situation into account, according to the present invention, guide rods which are guided in threaded bushings, are braced or bear against the bottom of threaded bushings by means of compression springs. The threaded bushings are threaded into holes in a cylinder portion of the cylinder channel and are adjustable in the clamping direction. The distance of the threaded bushings from the stationary clamping assemblies can, therefore, be changed merely by turning the threaded bushings in such a manner that the greatest possible spring tension is maintained in spite of the difierent length of the plate to be clamped.

Thicker plates cannot be sufficiently and firmly clamped on a cylinder by spring tension, particularly for long runs. and fatigue breaks of the plate may, therefore, occur due to the spring loading. For this reason. in a further embodiment of the present invention, there are at the rear of the displaceable clamping bar assembly one or several clamping spindles which extend parallel to the guide rods. The clamping spindles protrude through holes in a clamping rib provided in the cylinder channel and are equipped at their free end with a tensioning screw. The clamping operation can be performed relatively rapidly because the clamping nuts are not under tension over the major part of the screw travel as the spring-loaded guide rods already basically tension the plate.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described in relationship to specific embodiments, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

HO. 1 is a partial cross-sectional view of a cylinder with a clamping device according to one embodiment of the invention.

FIG. 2 is a top view of the cylinder and clamping device shown in FIG. 1, wherein the right half of the Figure shows the clamping bar assembly in the tensioning position and the left half of the Figure shows the clamping bar assembly in the non-tensioning position.

FlG. 3 is a top view of the cylinder showing the quickaction clamping and the clamping screw.

Referring to the drawings, FIG. 1 shows a clamping bar assembly 3 arranged in stationary relation in the channel 1 of a plate cylinder 2. The clamping bar assembly 3 consists of a lower clamping bar 4, an upper clamping bar 5 and a clamping eccentric 6. The clamping bar assembly 3 grips the rear end of a flexible plate 7.

A further clamping bar assembly 8 is provided on the opposite side of the cylinder channel 1. The clamping bar assembly 8 is displaceable along a secant on a sliding surface 9. In this case, the clamping bar assembly 8 consists similarly to the clamping bar assembly 3, of a lower clamping bar 10, an upper clamping bar 11, and a clamping eccentric 12. Both clamping bars 10 and 11 grip the front end of the flexible plate 7 which is to be clamped.

Two guide rods 14 and 15 are threadedly fastened to the rear 13 of the lower clamping bar 10. The guide rods l4, 15 extend parallel to the sliding surface 9 and each protrudes through a threaded bushing 16 and 17, respectively, in which they are guided. In each of the bushings 16 and 17, the guide rods 14 and 15 are surrounded by a compression spring 18 and 19, respectively, which are braced or bear against the bottom of the threaded bushings l6 and 17 and push or bear, on the other hand, against washers 20 and 21 attached to the free ends of the guide rods 14 and 15 respectively.

The threaded bushings l6 and 17 are screwed or threaded into holes 22 of a clamping rib 23 provided in the cylinder channel 1. The travel or displacement of the clamping bar assembly 8 as well as the desired spring tension for clamping the plate 7 can be set by adjusting the threaded bushings 16, 17. Depending on the length of the plate 7 to be clamped, the appropriate travel or displacement of the clamping bar assembly 8 is adjusted.

In the middle of the cylinder 2 there is provided a latch 25 which can be swung between two limit pins 26 and 27. The latch 25 is pivoted on the clamping rib 23 about an axis 24 extending perpendicularly to the axis of rotation of the cylinder 2. The clamping bar assembly 8 can be pushed, for example by hand, against a stop edge 28 on the cylinder 2 against the force of the two compression springs 18 and 19 for the purpose of clamping the flexible plate 7. In this position, the latch 25 rests against the limit pin 26. The latch 25, therefore, holds the clamping bar assembly 8 in a position in which the end of the plate 7 can conveniently be inserted between the clamping bars and 11. If the latch 25, however, rests against the limit pin 27 and if the clamping bar assembly 8 has not gripped a plate, the compression springs 18 and 19 can push the clamping bar assembly 8 only so far into the interior of the cylinder gap until stop pins 30 and 31, which are provided on the switching rods 14 and 15, rest against the threaded bushings [6 or 17 respectively.

At the same height as the latch 25, there is provided a clamping screw 33 which is screwed into the rear side of the lower clamping bar 10 just as the guide rods 14 and 15 are screwed into the clamping bar 10. The clamping screw 33 which passes through a hole 32 in the clamping rib 23 is disposed parallel to the guide rods l4 and 15. At the free end of the clamping screw 33 a clamping nut 34 is provided which may be screwed against the side of the clamping rib 23 facing away from the clamping bar assembly 8.

The operation of the device described is as follows. The rear end of the plate 7 to be clamped is gripped by the stationary clamping bar assembly 3 by appropriate rotation of the clamping eccentric 6. Then the movable clamping bar assembly 8 is pushed by hand against the bias of the compression springs 18 and 19 in the direction toward the stop edge 28. When the lower clamping bar It] engages the stop edge 28, the latch 25 drops into the left-hand position shown in FIG. 2, that is, the latch rests against the limit pin 26. The clamping bar assembly 8 is thereby held in a position by latch 25 in which the front end of the flexible plate 7 is clamped by the clamping bars 10 and I1 by turning the eccentric 12. Then the printer or operator only needs to hit the latch 25 or its switching pin 35 with the tool which he used to operate the eccentric 12, whereby the latch 25 is swung against the limit pin 27 and the compression springs 18 and 19 pull the clamping bar assembly into the cylinder gap so that the plate 7 is firmly tensioned on the circumference of the plate cylinder 2. This normally completes the clamping operation.

Due to the adjustability of the threaded bushings l6 and 17, flexible plates with a length difference of about mm may be clamped by means of the device according to the invention without the spring pressure required for tensioning becoming too low.

In the case where a relatively thick plate is to be clamped on the plate cylinder 2, the clamping nut 34 can be screwed additionally against the clamping strip 23 after this plate is tensioned by the compression springs 18 and 19, so that the thick plate 7 conforms closely to the contour and curvature on the circumference of the cylinder 2. The additional clamping by means of the clamping nut 34 is of advantage particularly in large installations in which plates which are not sufficiently clamped have a tendency to fracture due to premature fatigue. The tightening and loosening of this clamping nut 34 may be performed very rapidly because the compression springs 18 and I9 basically already tension the plate gripped by the clamping bar assemblies 3 and 8. The clamping nut 34 can, therefore, be adjusted for clamping as well as loosening without tension over the major part of the screw travel.

The invention is not limited to the embodiment shown. A modification is possible, for example, in that the latch 25 may be put under spring pressure and, therefore, snaps automatically against the limit pin 26 when the clamping bar assembly 8 is advanced.

I claim:

1. in a quick-action clamping device for use in rotary cylinders of printing machines for clamping flexible printing plates comprising a stationary and a secant displaceable clamping bar assembly disposed in a channel in the plate cylinder, said displaceable clamping bar assembly being adapted to be selectively held in a first position which applies tension to the pressure plate and in a second position which does not apply tension to the pressure plate; at least two guide rods affixed to the back side of the displaceable clamping bar assembly, said guide rods being constantly under spring tension in clamping direction of the plate, a latch pivotably mounted on an axis extending perpendicularly to the axis of rotation of said cylinder, a clamping rib provided in the channel of the plate cylinder, at least one clamping screw affixed to the back of the displaceable clamping bar assembly and extending parallel to said guide rods, said clamping screw extending through a bore of said clamping rib, said clamping screw having a clamping nut on its free end, bushings threadedly engaged in said clamping rib, said guide rods being guided in said bushings, springs disposed in said bushings, said bushings having a bottom portion against which said springs are biased, said bushing being threadedly adjustable in said clamping rib in a direction for applying tension to said plate.

2. A quick-action clamping device according to claim 1 including stop pins on said guide rods adapted to engage said bushings to limit the extent to which said push rods may be displaced longitudinally relative to said bushing. 

1. In a quick-action clamping device for use in rotary cylinders of printing machines for clamping flexible printing plates comprising a stationary and a secant displaceable clamping bar assembly disposed in a channel in the plate cylinder, said displaceable clamping bar assembly being adapted to be selectively held in a first position which applies tension to the pressure plate and in a second position which does not apply tension to the pressure plate; at least two guide rods affixed to the back side of the displaceable clamping bar assembly, said guide rods being constantly under spring tension in clamping direction of the plate, a latch pivotably mounted on an axis extending perpendicularly to the axis of rotation of said cylinder, a clamping rib provided in the channel of the plate cylinder, at least one clamping screw affixed to the back of the displaceable clamping bar assembly and extending parallel to said guide rods, said clamping screw extending through a bore of said clamping rib, said clamping screw having a clamping nut on its free end, bushings threadedly engaged in said clamping rib, said guide rods being guided in said bushings, springs disposed in said bushings, said bushings having a bottom portion against which said springs are biased, said bushing being threadedly adjustable in said clamping rib in a direction for applying tension to said plate.
 2. A quick-action clamping device according to claim 1 including stop pins on said guide rods adapted to engage said bushings to limit the extent to which said push rods may be displaced longitudinally relative to said bushing. 